Beschreibung:
<jats:p>Photorefractive effects of nominally pure and iron-doped KNbO3 crystals with concentrations between 150 and 300 ppm have been investigated. In order to optimize the photorefractive recording times and the amplitude of the refractive changes, the crystals were thermally treated with simultaneous photorefractive testing. The photoconductivity data and the photorefractive experiments (grating spacing dependence of the beam coupling gain) show that the relative influence of electron and hole contribution is altered depending on the reduction treatment. The experimental results are discussed with a two-carrier model.</jats:p>